The previous chapters of "One Piece" failed to reveal the ultimate fate of Sanji but as stated in a report from Design and Trend, Sanji will become the most important character in the upcoming chapter 812. It is reported that the chapter will focus on a flashback and will showcase his fight against Big Mom and her crew of pirates.

However, Sanji is already expected to be one of Big Mom's important prisoners. According to Movie News Guide, it is also possible that Sanji was able to set up a deal with the Pokems in order to make Big Mom and her crew of pirates leave Zou Island for good, taking him and Don Quixote Pirates' member Caesar along with them.

Of course with Sanji in their hands it is very likely that this will prompt the Straw Hats Pirates to wage a war against Big Mom and her crew. This is said to be one of the bigger fights in the current arc and is one of the most anticipated ones in the series thus far. 

Design and Trend also points out that Sanji's name is one of the most important in the current arc. His bounty lists him as "Wanted Alive" instead of "Dead or Alive" and he is notable for being the second captain of the Straw Hats when they disbanded several arcs ago.

A report from Youth Health Mag points out that Caesar is likely to become the tenth member of the Straw Hats team. Caesar Clown has helped the Straw Hats before, notably in the chapter prior to this and he may become a permanent member when he and Sanji are saved by Captain Luffy and the rest of the Straw Hats.

"One Piece" Chapter 812 is expected to release in the upcoming issue of Shonen Jump Magazine.